Compliant Guiding Catheter Sheath System

ABSTRACT

A guiding catheter system employs a compliant shaft with an inflatable balloon affixed to a distal portion of the shaft. The inflatable balloon includes channels that allow some amount of blood to flow past the balloon when inflated in a blood vessel. One or more inflation lumens is in fluid contact with the balloon and allows inflating the balloon from a proximal end of the catheter. A series of perfusion orifices may be included on the shaft proximal to the balloon.

RELATED PATENT DOCUMENTS

This is a divisional of U.S. patent application Ser. No. 10/424,333,filed on Apr. 28, 2003, to which Applicant claims priority under 35U.S.C. §120, and which is incorporated herein by reference

FIELD OF THE INVENTION

The invention relates generally to guiding catheter systems, and, moreparticularly, to guiding catheters for accessing the coronary sinus andother heart vessels.

BACKGROUND OF THE INVENTION

Guiding catheters are instruments that allow a physician to locate andcannulate vessels in a patient's heart for performing various medicalprocedures, including venography and implanting of cardiac pacingdevices. Cannulating heart vessels requires navigating a small diameter,flexible guide through convoluted vasculature into a heart chamber, andthen into a destination heart vessel. Once the destination heart vesselis reached, the catheter acts as a conduit for insertion of payloadsinto the vessel.

Once the vessel has been cannulated by a guiding catheter, an occlusiondevice may be utilized to hold the distal end of the guiding catheter inplace during various procedures. The occlusion device blocks blood flowthrough the vessel at the same time lodging the catheter in place.

However, the blood flow cannot be blocked indefinitely, as occlusion ofblood flow may cause detrimental effects on the patient. Therefore theclinician must be concerned about leaving the occluding device in placefor too long. There is a need in the art for an improved guidingcatheter for accessing heart vessels that can be guided through aconvoluted pathway and lodged for a longer period of time in a bloodvessel. The present disclosure discusses these and other needs in theart.

SUMMARY OF THE INVENTION

The present invention discloses a guiding catheter that can provideaccess to venous structures for medical procedures and be firmly lodgedin those vessels while still allowing some amount of blood flow in thevessels.

In one embodiment, a guiding catheter for use with a guide apparatus forcannulating a blood vessel includes a flexible shaft having an openlumen. The open lumen is placeable over the guide apparatus so that theflexible shaft substantially assumes the shape of the guide apparatus.The guiding catheter includes a balloon at a distal portion of theflexible shaft. The balloon includes one or more external channels. Aninflation lumen is disposed along the flexible shaft and in fluidconnection with the balloon. Pressurization of a fluid in the inflationlumen inflates the balloon. The inflated balloon is arranged to lodge inthe blood vessel and permit an external fluid flow through the externalchannels.

In one arrangement, the guiding catheter further includes one or moreperfusion orifices of the flexible shaft proximal to the balloon. Theperfusion orifices are in fluid connection with the external fluid flowand the open lumen of the flexible shaft. The balloon may be configuredto include a plurality of expansion lumens, the external channelsdefined between adjacent expansion lumens. In some arrangements, theballoon may include three or four expansion lumens. The three expansionlumen arrangement may be configured to define an approximatelytriangular cross sectional shape.

The external channels of the balloon may be oriented substantiallyparallel to a centerline of the flexible shaft. In another arrangement,the external channels include a helical channel extending from a distalend of the balloon to a proximal end of the balloon.

In another embodiment of the present invention, a method of cannulatinga destination vessel involves introducing a guide apparatus into thedestination vessel. A guiding catheter is placed over the guideapparatus so that a distal portion of the guiding catheter is disposedin the destination vessel. A balloon disposed on a distal portion of theguiding catheter may be inflated so that the distal portion of theguiding catheter is lodged in the destination vessel and an externalflow is permitted through an external channel of the balloon.

Introducing the guide apparatus in the destination vessel may involveactuating a steering mechanism of the guide apparatus to direct a distalend of the guide apparatus. In another arrangement, introducing theguide apparatus in the destination vessel involves manipulating apre-shaped distal portion of the guide apparatus to direct a distal endof the guide apparatus.

The above summary of the present invention is not intended to describeeach embodiment or every implementation of the present invention.Advantages and attainments, together with a more complete understandingof the invention, will become apparent and appreciated by referring tothe following detailed description and claims taken in conjunction withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cutaway view of a heart, showing a guiding catheteraccording to embodiments of the present invention deployed in the rightatrium;

FIG. 2 is a side view of a distal end of the catheter according toembodiments of the present invention;

FIG. 3 is a cross sectional view of the catheter and balloon of FIG. 2,corresponding to section 2-2 of FIG. 2;

FIG. 4 is a cross sectional view of the catheter shaft corresponding tosection 2-2 of FIG. 2 showing an alternate cross sectional shape of theballoon;

FIG. 5 is a side view of a distal end of a catheter illustrating ahelical channel arrangement according to embodiments of the presentinvention; and

FIG. 6 is a cross sectional view of the catheter showing perfusionorifices according to embodiments of the present invention.

While the invention is amenable to various modifications and alternativeforms, specifics thereof have been shown by way of example in thedrawings and will be described in detail herein. It is to be understood,however, that the intention is not to limit the invention to theparticular embodiments described. On the contrary, the invention isintended to cover all modifications, equivalents, and alternativesfalling within the scope of the invention as defined by the appendedclaims.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

In the following description of the illustrated embodiments, referencesare made to the accompanying drawings which form a part hereof, and inwhich is shown by way of illustration, various embodiments in which theinvention may be practiced. It is to be understood that otherembodiments may be utilized, and structural and functional changes maybe made without departing from the scope of the present invention.

In broad and general terms, a guiding catheter according to embodimentsof the present invention employs a flexible shaft having a balloonattached at a distal end. The balloon has channels that allow fluid toflow past the inflated balloon. The guiding catheter includes an openlumen in the flexible shaft adapted for the introduction of payloadsthrough the catheter system. The guiding catheter can be placed over asmaller maneuverable guiding apparatus that is used to locate a vessel.In one application, the guiding catheter can be used to introduce apayload into the coronary sinus or other heart vessels.

Turning now to FIG. 1, a guiding catheter, generally indicated byreference numeral 100, is shown deployed in the right atrium 101 of theheart. The guiding catheter 100 includes a flexible shaft 102 with anopen lumen, and an inflatable balloon 104 at a distal end of the shaft102. A distal tip 106 of the catheter 100 is positioned in the coronarysinus 108. The balloon 104 can be inflated to lodge the flexible shaft102 in the coronary sinus 108.

The balloon 104 contains channels 112 that allow an external flow ofblood to move past the lodged catheter shaft 102. In general, the term“external flow” as used herein generally refers to a flow past the outersurfaces of the catheter shaft 102 and the balloon 104. By providing abypass external blood flow, the balloon 104 can advantageously remaininflated in place for longer periods of time. Once the balloon 104 islodged into place, the flexible catheter shaft 102 can act as a guidefor other devices such as contrast media, implantable leads, anddiagnostic devices.

Implantation procedures may vary depending on the goal of the procedureand the condition of the patient. For purposes of example, one procedurefor implanting a pacing lead into the coronary sinus 108 will bedescribed in relation to FIG. 1. A maneuverable guide apparatus 122 mayfirst be guided into the right atrium 101 to locate the ostium 124 ofthe coronary sinus 108. The guide apparatus 122 may be any type ofpre-shaped and/or steerable apparatus. For purposes of illustration, theguide apparatus 122 will be described as a pre-shaped, steerableelectrophysiology (EP) catheter.

During the EP catheterization procedure, a clinician inserts the EPcatheter 122 into an access vessel 126 through an incision or introducersheath puncture 128. The access vessel 126 may include any of the largeveins of the upper limb system such as the cephalic or subclavian veins.Lower limb vessels such as the femoral artery are also used as accesspoints for many heart cannulation procedures.

Once the EP catheter 122 is in the right atrium, the shape and/orsteering apparatus of the EP catheter 122 may be used to assist inlocating the coronary sinus ostium 124. The EP catheter 122 may alsocontain distal electrodes (not shown) that assist in locating the ostium124. Signals from the electrodes can be used to “map” electricalactivity of the heart tissues. Once the clinician has found the coronarysinus ostium 124, the guiding catheter 100 may be slid over the EPcatheter 122 to introduce the guiding catheter 100 into the coronarysinus 108.

In an alternate approach to placing the guiding catheter 100 in thecoronary sinus 108, the guiding catheter 100 may be first introducedinto the access vessel 126 and into the right atrium 101. After thedistal tip 106 of the guiding catheter 100 is located in the rightatrium 101, the EP catheter 122 can be placed into the open lumen of theguiding catheter 100 so that the EP catheter 122 emerges into the rightatrium 101. The guiding features of the EP catheter 122 can then be usedto locate the coronary sinus ostium 124, after which the guidingcatheter 100 can be slid over the EP catheter 122 into the coronarysinus 108.

The flexible shaft 102 of the guiding catheter 100 is typically maderelatively compliant so that the shaft 102 can be placed over a guideapparatus without substantially disturbing the shape of the apparatus.This compliant shaft 102 also helps reduce anatomical trauma duringplacement procedures. Once the guiding catheter 100 is fully seated inposition, the balloon 104 can be inflated to hold the flexible shaft 102in place. The inflated balloon 104 provides the catheter 100 with ananchor point to prevent dislodgment of the shaft 102 during furtherprocedures.

Once the guiding catheter 100 is lodged into place, the EP catheter 122can be removed. The guiding catheter 100 remains as a conduit forpayloads directed to the heart. In one example, a contrast media can beinjected into the flexible shaft 102 for fluoroscopic mapping ofcoronary vessels. It is appreciated that the channels 112 of theinflated balloon 104 may allow some small amount of the contrast mediato flow out of the coronary sinus 108. However, the contrast media hassignificantly greater viscosity than blood, therefore this “backflow” ofcontrast media will be minimized.

After performing fluoroscopy, a device such as a pacing lead may beimplanted into a branch vessel of the coronary sinus 108. In oneprocedure, the pacing lead is inserted into the guiding catheter 100until in emerges into the coronary sinus 108. A stylet or guidewire maybe used to assist placing the pacing lead in the branch vessel. Afinishing wire or other fixing device can be inserted to hold the pacinglead into place, after which the balloon 104 can be deflated and theflexible shaft 102 of the catheter 100 withdrawn. The shaft 102 mayinclude peel away features such as a longitudinal pre-stress on theshaft walls that allow the shaft 102 to be peeled apart as it iswithdrawn. Finally, after withdrawing the shaft 102, the finishing wireor fixing device is removed to complete the procedure.

Turning now to FIG. 2, construction details of the guiding catheter 100are illustrated. The shaft 102 is typically an elongated tubular memberhaving an open guide lumen 202. The guide lumen 202 is formed to allowthe shaft 102 to be introduced over guide apparatus as well as acting asa conduit for payloads introduced into the catheter 100.

The balloon 104 is fixably mounted at a distal portion of the shaft 102.The balloon 104 is in fluid contact with one or more inflation lumens204 used to inflate and deflate the balloon 104. The inflation lumens204 may be formed on an inside or outside surface of the flexible shaft,or the inflation lumens 204 may be formed within the walls of theflexible shaft 102. The inflation lumens 204 are accessible from theproximal end of the catheter 100, thereby allowing the clinician toinflate and deflate the balloon 104 using a proximal device such as asyringe.

The balloon 104 contains channels 112 that allow blood flow to bypassthe inflated balloon 104. In FIG. 2, these channels 112 are orientedapproximately parallel to the centerline of the shaft 102. Thisorientation of the channels 112 is typical, since it also corresponds tothe direction of blood flow in the blood vessel. However, otherorientations of the channels 112 may be used, assuming the channels 112allow blood to flow past the inflated balloon 104.

The balloon 104 may be fabricated with any suitable cross sectionalshape. Two exemplary cross sectional shapes are shown in FIGS. 3 and 4.In FIG. 3, the balloon 104 includes a substantially triangular crosssectional shape. The balloon 104 includes three expansion lumens 302that expand to lodge against the walls of a blood vessel. The channels112 are defined by the spaces between the expansion lumens 302. Theballoon 104 may be bonded or otherwise affixed to the shaft 102 atportions of the balloon 104 that define the channels 112. The expansionlumens 302 may be in fluid connection with each other and the inflationlumens so that all expansion lumens 302 inflate simultaneously.Alternatively, each lumen 302 may have an associated inflation lumen sothat each expansion lumen 302 is independently inflatable.

The flexible shaft 102 as illustrated in FIG. 3 may include an innerliner 304 and an outer sheath 306. The inner liner 304 may be formed ofa lubricious material such as polytetrafluoroethylene (PTFE). The outersheath 306 may be fabricated of a smooth, wear resistant polymermaterial. The distal tip 106 of the shaft (see FIG. 2) may include asoft covering to prevent tissue trauma when introducing the catheter 100into blood vessels. The flexible shaft 102 may include other featuressuch as a stainless steel braiding (not shown) embedded within the shaftwalls to improve lateral and torsional stiffness.

In some configurations, the flexible shaft 102 is made withoutsignificant stiffening features such as a braid. A relatively compliantflexible shaft 102 can be made to more easily slide over an EP catheteror other guide apparatus. A compliant shaft 102 is less likely to“overpower” the shape of a guide apparatus in such a situation and isless likely to induce tissue trauma along the guide path. Finally, acompliant shaft 102 is more easily withdrawn and easier to peel awayshould a pre-stress feature be included in the shaft walls.

Because the catheter 100 can be introduced over a guide apparatus, theflexible shaft 102 can be made without any pre-shaped curve or variableflexibility along the shaft's length. This allows the catheter 100 to befabricated for general-purpose use. In general, the catheter 100 can beused with any guide apparatus that will fit within the guide lumen 202of the catheter 100.

Turning now to FIG. 4, a four-lobed balloon 104 is illustrated. As withthe triangular shape of FIG. 3, the portions of the balloons definingthe channels 112 may be bonded or otherwise fixed to the shaft 102. Thefour expansion lumens 302 may be in fluid connection with each other orindependently inflatable.

Although the channels 112 may be oriented substantially parallel to thecenterline of the flexible shaft 102, other channel orientations may bepossible. For example, FIG. 5 shows a helical channel 112 extendingalong the balloon 104. Such a helical channel 112 may provide theballoon 104 with a more secure contact surface when the balloon 104 isinflated in a blood vessel.

Additional features may be included with a catheter 100 according toembodiments of the present invention to increase the amount of bypassblood flow. For example, FIG. 6 shows a cross sectional view of a distalportion of the catheter's flexible shaft 102. A series of perfusionorifices 602 are included on a portion of the shaft walls proximate theballoon 104. The perfusion orifices 602 are in fluid connection with theguide lumen 202 and an external flow outside the flexible shaft 102.

Blood can enter the guide lumen 202 through the distal tip 106 of theflexible shaft 102 and can exit through the orifices 602 as indicated bythe bold arrows. Blood can also flow in a direction opposite thatindicated by the arrows. The effectiveness of the perfusion orifices 602may depend on the size of any payload deployed within the catheter 100,as large payloads may block the guide lumen 202 to some extent. It isappreciated that the combination of bypass features of the balloon 104and the perfusion orifices 602 may provide enhanced bypass blood flow inmany applications.

From the description provided herein, those skilled in the art arereadily able to construct and use a guiding catheter according toembodiments of the present invention. It will, of course, be understoodthat various modifications and additions can be made to the preferredembodiments discussed hereinabove without departing from the scope ofthe present invention. Accordingly, the scope of the present inventionshould not be limited by the particular embodiments described above, butshould be defined only by the claims set forth below and equivalentsthereof.

1. A guiding catheter system for cannulating a coronary sinus of apatient's heart, the guiding catheter system comprising: a guideapparatus comprising a distal end having a pre-shaped curve shaped forcannulating the coronary sinus from the right atrium; a flexible shafthaving an open lumen dimensioned to receive and allow an implantablepacing lead to be passed through the flexible shaft, the guide apparatusand the flexible shaft configured such that the open lumen of theflexible shaft is slidable over the guide apparatus; an inflation lumenarrangement disposed along the flexible shaft; and a balloon arrangementprovided at a distal portion of the flexible shaft and circumferentiallysurrounding the distal portion of the flexible shaft, the balloonarrangement fluidly coupled to the inflation lumen arrangement andcomprising: a plurality of expansion lumens extending generally axiallyalong a longitudinal length of the distal portion of the flexible shaftand spaced circumferentially apart from one another; a plurality ofexternal channels defined between adjacent expansion lumens of theplurality of circumferentially spaced-apart expansion lumens andextending continuously and generally axially along the longitudinallength of the distal portion of the flexible shaft; a plurality ofcircumferentially spaced-apart contact regions defined generally axiallyalong an apical portion of the expansion lumens and configured tocontact portions of an inner wall of the coronary sinus; the pluralityof expansion lumens, when in an inflated configuration, having adiameter greater than respective diameters of the distal portion of theflexible shaft and the plurality of external channels and sufficient tofacilitate anchoring of the flexible shaft within the coronary sinus bycontact between the plurality of contact regions and the portions of theinner wall of the coronary sinus; and the plurality of externalchannels, when the plurality of expansion lumens are in the inflatedconfiguration, facilitating transport of blood along the externalchannels and past the balloon arrangement sufficient to preventocclusion of blood flow through the coronary sinus that can causedetrimental effects on the patient.
 2. The system according to claim 1,wherein the plurality of expansion lumens, when in the inflatedconfiguration, urge the distal portion of the flexible shaft radiallyinward within a lumen of the coronary sinus and away from the inner wallof the coronary sinus.
 3. The system according to claim 1, wherein theplurality of expansion lumens, when in the inflated configuration, urgethe distal portion of the flexible shaft away from the inner wall of thecoronary sinus and to a position within a lumen of the coronary sinussuch that a central longitudinal axis of the flexible shaft is generallyaligned with a central longitudinal axis of the lumen of the coronarysinus.
 4. The system according to claim 1, wherein the plurality ofcontact regions, when the plurality of expansion lumens are in theinflated configuration, facilitate anchoring of the flexible shaftwithin the coronary sinus with sufficient force to prevent dislodgementof the flexible shaft when the guide apparatus is removed from theflexible shaft.
 5. The system according to claim 1, wherein theplurality of contact regions, when the plurality of expansion lumens arein the inflated configuration, facilitate anchoring of the flexibleshaft within the coronary sinus with sufficient force to preventdislodgement of the flexible shaft when the guide apparatus is removedfrom the flexible shaft and when the implantable pacing lead is advancedthrough the open lumen of the flexible shaft and to the coronary sinus.6. The system according to claim 1, wherein the flexible shaft comprisesa material having a flexibility greater than a material from which theguide apparatus is formed, such that the flexible shaft substantiallyassumes the shape of the guide apparatus without disturbing the shape ofthe guide apparatus when the flexible shaft is slid over the guideapparatus.
 7. The system according to claim 1, wherein the flexibleshaft is devoid of a distal pre-shaped curve and comprises a materialhaving a flexibility greater than a material from which the guideapparatus is formed, such that the flexible shaft substantially assumesthe shape of the guide apparatus without disturbing the shape of theguide apparatus when the flexible shaft is slid over the guideapparatus, and the distal portion of the flexible shaft assumes a shapeof the pre-shaped curve of the distal end of the guide apparatus.
 8. Thesystem according to claim 1, wherein the flexible shaft comprises one ormore perfusion orifices proximal to the balloon arrangement and in fluidcommunication with the external blood flow and the open lumen of theflexible shaft.
 9. The system according to claim 1, wherein the flexibleshaft comprises one or more peel features longitudinally disposed alongthe flexible shaft.
 10. The system according to claim 1, wherein theflexible shaft comprises one or more peel features longitudinallydisposed along the flexible shaft and the flexible shaft has variableflexibility along its length.
 11. The system according to claim 1,wherein the flexible shaft, inflation lumen arrangement, and balloonarrangement define components of a guiding catheter.
 12. The systemaccording to claim 1, wherein the guide apparatus further comprises asteering mechanism configured to facilitated user maneuvering of thepre-formed curve of the distal end of the guide apparatus from aproximal location of the guide apparatus.
 13. A guiding catheter systemfor cannulating a coronary sinus of a patient's heart, the guidingcatheter system comprising: a guide apparatus comprising a distal endhaving a pre-shaped curve shaped for cannulating the coronary sinus fromthe right atrium; a flexible shaft having an open lumen dimensioned toreceive and allow an implantable pacing lead to be passed through theflexible shaft, the guide apparatus and the flexible shaft configuredsuch that the open lumen of the flexible shaft is slidable over theguide; an inflation lumen arrangement disposed along the flexible shaft;and a balloon arrangement provided at a distal portion of the flexibleshaft and circumferentially surrounding the distal portion of theflexible shaft, the balloon arrangement fluidly coupled to the inflationlumen arrangement and comprising: one or more expansion lumens extendinggenerally axially along a longitudinal length of the distal portion ofthe flexible shaft; at least one external channel extending continuouslyalong the longitudinal length of the distal portion of the flexibleshaft and having a generally helical shape; a plurality of spaced-apartcontact regions defined generally axially along an apical portion of theone or more expansion lumens adjacent to the at least one externalchannel and configured to contact portions of an inner wall of thecoronary sinus; the one or more expansion lumens, when in an inflatedconfiguration, having a diameter greater than respective diameters ofthe distal portion of the flexible shaft and the at least one externalchannel and sufficient to facilitate anchoring of the flexible shaftwithin the coronary sinus by contact between the plurality of contactregions and the portions of the inner wall of the coronary sinus; andthe at least one external channel, when the one or more expansion lumensare in the inflated configuration, facilitating transport of blood alongthe at least one external channel and past the balloon arrangementsufficient to prevent occlusion of blood flow through the coronary sinusthat can cause detrimental effects on the patient.
 14. The systemaccording to claim 13, wherein the one or more expansion lumens, when inthe inflated configuration, urge the distal portion of the flexibleshaft radially inward within a lumen of the coronary sinus and away fromthe inner wall of the coronary sinus.
 15. The system according to claim13, wherein the one or more expansion lumens, when in the inflatedconfiguration, urge the distal portion of the flexible shaft away fromthe inner wall of the coronary sinus and to a position within a lumen ofthe coronary sinus such that a central longitudinal axis of the flexibleshaft is generally aligned with a central longitudinal axis of the lumenof the coronary sinus.
 16. The system according to claim 13, wherein theplurality of contact regions, when the one or more expansion lumens arein the inflated configuration, facilitate anchoring of the flexibleshaft within the coronary sinus with sufficient force to preventdislodgement of the flexible shaft when the guide apparatus is removedfrom the flexible shaft.
 17. The system according to claim 13, whereinthe plurality of contact regions, when the one or more expansion lumensare in the inflated configuration, facilitate anchoring of the flexibleshaft within the coronary sinus with sufficient force to preventdislodgement of the flexible shaft when the guide apparatus is removedfrom the flexible shaft and when the implantable pacing lead is advancedthrough the open lumen of the flexible shaft and to the coronary sinus.18. The system according to claim 13, wherein the at least one externalchannel having the helical shape completes at least one revolution ofthe balloon arrangement.
 19. The system according to claim 13, whereinthe at least one external channel having the helical shape completes atleast two revolutions of the balloon arrangement.
 20. A guiding cathetersystem for cannulating a coronary sinus of a patient's heart, theguiding catheter system comprising: a guide apparatus comprising adistal end having a pre-shaped curve shaped for cannulating the coronarysinus from the right atrium; a flexible shaft having an open lumendimensioned to receive and allow an implantable pacing lead to be passedthrough the flexible shaft, the guide apparatus and the flexible shaftconfigured such that the open lumen of the flexible shaft is slidableover the guide; an inflation lumen arrangement disposed along theflexible shaft; and a balloon arrangement provided at a distal portionof the flexible shaft and circumferentially surrounding the distalportion of the flexible shaft, the balloon arrangement fluidly coupledto the inflation lumen arrangement and comprising: one or more expansionlumens extending generally axially along a longitudinal length of thedistal portion of the flexible shaft; at least one external channelextending continuously along the longitudinal length of the distalportion of the flexible shaft; a plurality of spaced-apart contactregions defined generally axially along an apical portion of the one ormore expansion lumens adjacent to the at least one external channel andconfigured to contact portions of an inner wall of the coronary sinus;the one or more expansion lumens, when in an inflated configuration,having a diameter greater than respective diameters of the distalportion of the flexible shaft and the at least one external channel andsufficient to facilitate anchoring of the flexible shaft within thecoronary sinus by contact between the plurality of contact regions andthe portions of the inner wall of the coronary sinus; and the at leastone external channel, when the one or more expansion lumens are in theinflated configuration, facilitating transport of blood along the atleast one external channel and past the balloon arrangement sufficientto prevent occlusion of blood flow through the coronary sinus that cancause detrimental effects on the patient.